Each killer is a role player in a very different way, in part describing America's dilemma, in part describing America's future. A Central Asian guerrilla who ran jihad camps in Afghanistan. A Palestinian nationalist in a safe house in the West Bank. A foiled Kurdish assassin gloating while awaiting execution in Iraq. And then there was Ayub. He represents it all: the academy, the curriculum, the origins, the boldness, the patience, the infinitely transmutable and unvanquished idea of jihad. This is a story about these killers, and of a journey through the mujahideen's world that began when the passenger jets struck.

The journey actually began long before that. I am a former Marine Corps captain, drawn to uniform two decades ago in part by the destruction of the Marine barracks in Beirut in 1983. I was a college student that fall. The cold war was still on, in all its rhetoric and force, and as I flipped through coverage of the bombing in a wrinkled copy of Newsweek left on a fraternity-house table, I became perplexed enough about what drove this suicidal new enemy against these young marines, men my own age, that the next academic year I signed up, pulled by curiosity, perhaps misplaced, through weapons and tactics training to the infantry ranks. After nearly seven years, including a tour in the Persian Gulf war, I drifted from government work, becoming a newspaper reporter and setting aside most thinking about war. That changed early on September 11, 2001, when a routine assignment for The New York Times put me in lower Manhattan just before two hijacked passenger jets knocked down the World Trade Center, in whose remains I labored for twelve days. In the following months the newspaper dispatched me to Uzbekistan, Tajikistan, Afghanistan, Jerusalem, the West Bank, the Gaza Strip, and now through Iran to Kurdish Iraq, perhaps the most politically isolated place in the world. On each of these assignments I chased stories, trying to understand an expanding war. Along the way, I was drawn back to 1983, to images of Beirut, and to the question I had asked myself before I signed up.

Sarget, Iraq, February 8, 2003

On a gray afternoon during the run-up to another war, a convoy of Land Cruisers halted on a dirt track near Iraq's northeastern border with Iran, beside an Arabic sign informing visitors they had arrived at the garrison of Ansar al-Islam's Victory Brigade. A large man in a camouflage jacket and a black-and-blue scarf stepped from his jeep and introduced himself as Ayub Hawleri. The name was a deceit. With his fierce eyes and flowing brown beard, Hawleri was better known, among his proteges and to the Kurdish intelligence officers who hoped to kill him, as Ayub Afghani, a nod to his experience as a guerrilla fighting the Soviet army in Afghanistan. Afghani had just led a convoy past bunkers crowded with brooding black-eyed gunmen and sites he forbade visitors to photograph: fighters' caves cut into a ridge, the sun-bleached foundations of a village razed by Saddam Hussein, a freshly dug martyrs' cemetery beneath crags often shrouded in clouds. By this time, I was in my third month in northern Iraq and had written about Ansar's violence and jihad politics in the Times. I was concerned the mujahideen knew who I was; I thought of their record of kidnapping, bombings, summary execution, and torture. As the convoy bounded over the uneven road, a bullet-riddled white pickup truck with its leering fighters rumbled beside us. The gunmen stared at us and smirked.

I had sat expressionless for most of the trip. When the fighters looked away, I turned to Jeffrey Fleishman, a correspondent for the Los Angeles Times. "I'm scared," I said.

Fleishman answered, without moving his head, "So am I."

The drive ended at a fortress enclosed by a fence bearing signs painted with red skulls, land mines, and crossed bones. Afghani strode the grounds, light-footed, surveying us with confidence and disgust. "Everything you hear about us is rumor," he said.

The battle for Iraq was soon to begin, but the outcome was not in doubt. Baghdad would fall. The larger war was here, in these mountains, against these ever-adapting mujahideen. Afghani was an archetype of a larger Islamic adversary — the unintended consequence of a dated American policy, a man who had acquired a suite of lethal tricks and developed cosmopolitan associations. He and the others I encountered gave shape to much of the new enemy arrayed against the West: the sophisticated simplicity of his fighting skill, the ease of assembly of his weapon of choice, the complexity of his anger, the forlorn state of the societies he springs from, the vastness of his recruiting pool. By now Osama bin Laden and his intentions were broadly understood. But what about the men who served him, who filled movements whose ranks were becoming as formless as smoke?

This was the new war of our lifetime.

And like the concept of jihad itself, Afghani was a survivor, a changeling. Once he had acted roughly in the security interests of the United States, helping roll back Soviet occupation in Afghanistan. But upon returning to Iraq, he insinuated himself among militant bands that had sprouted in these mountains. Ultimately he became a leader of Ansar, a gruesomely violent organization formed in 2001 when several parties merged. He served as the group's chief bomb maker and as an instructor in its academies of jihad.

Ansar was neo-Taliban, copying the Taliban's notions of ancient social order while operating Web sites that railed against Christians, Jews, and secular rule. Kurdish villages were filled with chatter of adherents splashing acid on women who ventured outside unveiled; Kurdish bazaars sold videos showing the mujahideen's enthusiasm for executing prisoners and mutilating their remains. In an address earlier this week to the United Nations Security Council, Secretary of State Colin Powell displayed a satellite image of this compound and declared it a poison factory and terrorist training camp. Ayub Afghani, erstwhile American ally, had become a reason for war.

Now he offered the key to this secret place. "You can search as you like," he said, and we moved past him, tentatively, into another campus in the university of international jihad.

New York City, September 11, 2001

Sixteen minutes after American Airlines flight 11 struck the North Tower of the World Trade Center, an immense flash erupted high in the second tower, followed by a blossoming orange explosion and a cascade of metal and glass. Pedestrians bolted on sidewalks below, some silent, some snorting, a few shrieking while sprinting as the explosion roared.

After the thunder had subsided and the first pieces of skyscraper showered the ground, people reemerged, peering from under scaffolding, stepping from doorways, unclasping from one another's grasp. Few among us knew what had happened. The impact of the first jet had seemed a horrific accident, the second blast a complete unknown. People milled near Liberty and Church streets, eyes skyward, mesmerized by fire.

I had been running to the South Tower when the second jet arrived. Now I tried to interview survivors: one man narrowly avoided the debris shower; another had stayed up late the night before watching the New York Giants on Monday Night Football and never made it to his desk; a third had gone to synagogue and missed a connecting train in Queens, an inconvenience that prevented him from reaching his office on the South Tower's one-hundredth floor, where he would now have been trapped above flame. Into this crowd walked Christopher Szymanski, who had disembarked minutes before from the ferry at Battery Park. He wore a jacket and tie. His blond hair was neat. He said he had been watching the first fire when a second plane appeared, low and fast. "I thought maybe it was the police and they were investigating," he said. We looked at him. A second plane? "I saw it go directly into the World Trade Center," he said.

People jostled past, weeping. Abandoned cars, some with doors open, were pell-mell on the street. Bits of the South Tower were peeling off. Standing beneath flames and pulsing smoke, ash settling on shoulders, bedlam all around, we peered at this curiously collected man. He had proof. "A wheel, a part of the plane, came right down and hit the lamppost and took it out," he said. "C'mon, I'll show it to you."

Szymanski had seen a wheel.

So began the first instant of understanding.

There had been a second plane.

This was not an accident.

With the attacks on September 11, small groups of men trained in little more than religious certitude and military fundamentals in distant, primitive camps did what no other movement had been able to do: They changed the relationship between the most powerful nation on earth and the rest of the world.

But the most ominous aspect of this newly expressed Islamic terror cannot be found in the malevolence of murders already committed, in the size of underground networks planning more attacks, or even in warnings that Osama bin Laden regards it as a religious duty to obtain a radiological device. It emerges in demographics.

There are roughly 1.2 billion Muslims in the world, one fifth of human life, concentrated in a swath of the planet extending from Morocco and sub-Saharan Africa northward and eastward beyond the Indonesian archipelago. Across much of this belt, living conditions are deplorable, economies narrow, and governments corrupt, repressive, and exempt from the rigors of democracy. This is the clay from which the West's enemy is made. Put yourself in the position of an eighteen-year-old Muslim now surveying prospects for life. Looking for work? The United Nations Arab Human Development report noted this year that Arab states, population 280 million, have a combined gross domestic product smaller than Spain's. Seeking education? Many Muslim governments are so dysfunctional and their citizens' rights and opportunities so limited that nearly 40 percent of the people in Arab states are illiterate. Expecting change? Open elections barely exist, even among Washington's partners. (In Uzbekistan, President Islam Karimov was reelected in 2000 with 91.7 percent of the vote, a tally not much different from Saddam Hussein's 99.96 percent in 2002; in Iraqi Kurdistan, often touted as the region's democratic beacon, there have not been parliamentary elections since 1992; in Saudi Arabia, where fifteen of the nineteen hijackers were born, there are no elections at all.)

Moreover, the Muslim world is gripped by a population boom, making it remarkably young. Nearly two thirds of Muslims are younger than thirty-five, according to the Population Reference Bureau; more than 35 percent have not yet turned fifteen. These conditions are apparent in alleys in Dushanbe, Baghdad, and Kabul; refugee camps in Afghanistan, western Pakistan, and Gaza; tenements in Tehran. In all of these places, children swarm. The risks are self-evident: A surge of Muslim youth is coming of age in places that cannot support it, and if young Muslims cannot attend school or expect a job or live in cities not stalked by crime, corruption, and disease, or vote for (or against) legislators or executives who take responsibility for their society's condition, and are exposed to media bristling with anti-Western reports, as they are, then the next generation of young Muslims risks being a recruiting pool for many times more terrorists than the West has yet seen.

And as each new devotee raises his hand for jihad, the jihad awaits, ready.

Kunduz, Afghanistan, November 29, 2001

My first trip into campuses of what I have come to see as a university of international jihad came soon after the Trade Center collapsed, in Juma Namangani's houses in Afghanistan.

Chang Lee, a New York Times photographer, and I had entered Afghanistan by barge, crossing from Tajikistan, and as the Taliban evaporated, we accompanied Northern Alliance commanders through seized terrain to Namangani's houses in Kunduz and Mazar-i-Sharif, which served as institutes of unconventional war. Trash and ammunition cluttered the courtyards; sacks of anti-Western pamphlets and Korans filled rooms inside. Everywhere was the refuse of jihad: correspondence, maps, training records, personnel files, student notebooks, course curricula, movement edicts, personal letters.

If jihad was a route to "the shade of Paradise's trees," as one militant wrote, this was a joyless log of the journey. One letter was a leader's appeal for shoes. Another recorded a physician's effort to save a jihadi's infant son. The child had been born prematurely. The doctor had only multivitamins. Survival was in doubt. "He became a little bit better," it read. "He became bad once again." The group also stored pamphlets railing against Israel and America, as well as song, smoke, sex, and drink. A radio script said the Northern Alliance wanted "to sell Afghanistan to America's Jews" and described American soldiers as sons of GIs in Vietnam who "tore open the stomachs of pregnant women and took the baby child, bayoneted the baby and held it up." Forms required recruits to provide information about potential targets — military bases, bridges, factories, police stations, power plants, reservoirs, television and radio stations — in their hometowns. (Western officials later said these forms served dual purposes: They identified which recruits were smart, and they exacted loyalty. "Once you get a kid to turn over an intelligence brief like that, you own him," one said. "He can never go home.")

Namangani, a famed Islamic guerrilla commander, had started his martial career as an adversary of Ayub Afghani, serving as a Soviet paratrooper in Afghanistan. Then he found faith. A member of an elite unit, he was from the Ferghana Valley, where Islam had endured under socialism's enforced atheism. Fighting against religious guerrillas radicalized Namangani, attracting him to the Islamists' side. Following Uzbekistan's break from Moscow in 1991, the new government cracked down on Islam again; Namangani began staging raids against his own land. His group took the name Islamic Movement of Uzbekistan, vowed to overthrow Uzbekistan, and established these training camps in Afghanistan, the center of international jihad preparation.

The movement's fighters were not exceptional — "I had the pleasure of observing IMU units, and they were cheap copies of Soviet paratroopers," an American intelligence officer told me — but they were fit and competent, and their persistence made them a mythic presence, homegrown holy warriors who embarrassed Central Asian states. American intelligence officials say that in 2001, Mullah Omar, the Taliban's leader, pressed the group to help in the civil war against Ahmed Shah Massoud and the Northern Alliance. Later Omar appointed Namangani to command the 055 Brigade, the Taliban's formation of foreign mujahideen.

It was an impossible task. In less than a year, Namangani had gone from being a guerrilla raiding Uzbekistan to fighting a land war against the United States. He was caught in a bombardment on November 18; American officials say he died the next day. Kundu-z fell soon after.

As Chang and I sat on the floor of Namangani's study flipping through his books, I recognized the material immediately. Much of what was in the jihadi pamphlets and books I knew from my own study in Marine Corps schools and the Army's Ranger course. Here a notebook contained diagrams for rigging mines and booby traps, there instructions for mixing Molotov cocktails or for connecting explosives to a timed fuse. Almost all of Namangani's books covered infantry arms, tactics for small units, and improvised demolitions. Some contained handwritten firing tables for mortars; one had four-man patrolling formations cribbed from the Marines and a reconnaissance technique used by Army Rangers. It was a primer for unconventional warfare, reduced to simple themes, composed in Tajik, Dari, Uzbek, and Arabic.

Intelligence officials knew Al Qaeda used manuals called the Encyclopedia of the Jihad to shape terrorist action. But the encyclopedia had several thousand pages. No school could teach every lesson from so large a collection. Here were the essentials: distilled, compact, practical, multilingual. It was a curriculum built to travel, ready for war against the West.

Nablus, West Bank, April 22, 2002

Beyond the well-crafted simplicity of the jihadi regimen, the striking aspect of Namangani's material was its appropriation of anti-Israel themes. Uzbeks and Tajiks, the bulk of IMU's membership, have no connection to Palestinians and yet the Palestinian cause helps motivate their fight.

This cross-pollination of the jihad was demonstrated for me months later by a Palestinian terrorist in the West Bank. To find him we followed a guide through alleys to a door obscured by a hanging blanket, slipped into the apartment, continued through a smoky room of men who barely looked up, across a kitchen crowded with women, and stopped upstairs in a small room, where a thin and intent young man sat on a purple plastic lawn chair. He was in his socks. At his side was a homemade hand grenade and a pistol with three loaded magazines.

The man said for the purposes of this conversation his name was Abu Mujahed. A nom de guerre was necessary, he said, because both the United States and Israel consider Al Aqsa Martyrs Brigade, of which he was a midlevel commander, to be a terrorist organization. In a corner the Arab News Network played on a small television, a loop of violence and grief: Palestinian boys throwing stones at tanks, an injured Arab writhing, widows, corpses, gurneys, guns. A young man served cups of steaming sweet tea.

Why, Mujahed said, didn't Washington acknowledge that war here fueled Muslim anger everywhere, which Al Qaeda harnessed and channeled against the United States? By this time the second Palestinian intifada was in its twenty-first month, and nearly 400 Israelis and 1,360 Palestinians had been killed. In March and April the Israel Defense Forces had raided Palestinian cities, capturing militants, seizing bomb laboratories, and enforcing curfews on neighborhoods and refugee camps. Schools closed. Hospitals crowded with men with infected wounds. Palestinian Authority offices were sacked. When we walked through the Palestinian governor's compound, we found the main building blasted with tank fire and a suite once used by Yasir Arafat gutted: drop ceiling torn down, the mattress on Arafat's bed ripped by bayonets, toilet shattered, washroom mirrors pulverized. Arafat's portrait bore a bullet hole in the forehead.

But they hadn't gotten Abu Mujahed, and now he sat in his lawn chair sipping his tea, grading the Israeli attack: meaningless. Men who embraced suicide missions were untroubled by the battlefield deaths of peers. There would be more fighters to replace the dead and injured, he said, and the loss of munitions labs was unimportant. They could be reestablished anywhere. "It is very easy to make a bomb," he said. I recalled the anti-Israeli literature in Namangani's camps, possessed by men who might have trouble finding Israel on a map and had ample local problems of their own. I remembered Osama bin Laden on Al Jazeera as the first bombs fell on Afghanistan. "America will never taste security and safety," he said, "unless we feel security and safety in our land and in Palestine."

Abu Mujahed pulled a ski mask over his face, picked up a rifle, and pumped it in the air. "If peace does not come now, for this generation, it is going to be very hard in the future," he said. "Hatred now will last for hundreds of years."

It is very easy to make a bomb."

The weapons of choice. No arms protocol can regulate them. Very little can be done to guard against them. The West will be seeing them for however many decades this war lasts, for the unalterable reason that they are simple to make. In one well-established form, a flash of heat or an electric spark is delivered to a bit of explosive called a booster, which has been packed against a larger, more stable explosive called the main charge. A pop like a firecracker sets off enormous destruction.

The trick for bomb makers is to control initiation: first for safety during assembly, ultimately to select the place and instant of its havoc. This is easy enough. A common method is to run paired electric wires to the booster, being careful to leave the circuit open, and then to connect the wires to a battery pack that will deliver the spark. The open circuit is the trigger. Close it, the bomb explodes. Bombers willing to be within the blast area often use switches removed from flashlights or doorbells. They need only arrive at a target, depress a button, and — job done. For those not seeking to die in the commission of their crime, ways exist to achieve distance. A modified wristwatch can serve as a timer. The control panel and receiver from a radio-powered toy, like the electric cars sold at Toys R Us, can be enlisted as a remote. One afternoon in the West Bank, an engineering officer in the Israel Defense Forces showed me how Palestinian terrorists wire bombs to the vibration function on mobile telephones. When a bomber calls a telephone rigged this way, the phone's battery sends an electric pulse down the wires. Boom.

High explosives rush violently outward when detonated, sending a wave of pressure and heat in all directions, along with bits of the object — suitcase, briefcase, car, man — that held the bomb. The detonating velocity of trinitrotoluene, TNT, is twenty-three thousand feet per second, a rate of travel that means no one in a blast's radius can spare themselves with a timely athletic dodge. But few who trouble with making bombs settle for simplicity. Bomb makers like frills: shards of glass or metal bolts as extra shrapnel, insecticide or rat poison as toxin, containers of fuel mixed with soap as incendiary jelly. One possibility now routinely discussed in law-enforcement circles involves packing radiological material, such as the soft white metal cesium-137, around the main charge. Cesium-137, commonly used for medical-radiation treatments, is available in most American cities. Very high exposure to it causes fatal burns. If a bomb packed with cesium-137 were to detonate, it would blow the isotope through the area and set it loose upon the wind. The isotope's half-life is 30.17 years. Hence the name: dirty bomb.

Since high explosives can be made with common chemicals, and boosters can be gathered by removing powder from fireworks or rifle bullets or scraping incendiary material from matchstick tips, once a bomb maker comprehends basic recipes, everything can be purchased at the bazaar. Al Aqsa often uses scored pipes packed with TATP, which is made with acetone, peroxide, and other available products. Ahmed Ressam, who planned to bomb Los Angeles International Airport during the millennium celebrations, made an explosive in part by mixing hydrogen peroxide with camp-stove tablets; demolitions experts who examined it said it would have worked. Timothy McVeigh created a forty-eight-hundred-pound charge by mixing ammonium-nitrate fertilizer with drag-racing fuel.

Becoming a bomb maker is not difficult. Principles of bomb craft can be gleaned from manuals used by civilian demolition companies, from engineering and chemistry textbooks, or from such antiestablishment how-tos as The Anarchist Cookbook, which is sold on Amazon.com.

Practical instruction is also found in readily purchased U. S. Army manuals, including three from the Vietnam War: Boobytraps, Explosives and Demolitions, and the Improvised Munitions Handbook. Page 69 of Boobytraps contains a drawing of about twenty people standing outside a three-story building. Smoke pours from windows. Several women, apparently civilians, are among the bystanders. An undetonated bomb is represented in the foreground by a box bearing the word explosive. The text reads: "A double delay chain detonating boobytrap should be very effective if timed right and skillfully laid. First, there is the explosive of a minor charge laid in an upper story damaging the building only slightly. Then, after a curious crowd has gathered, a second heavy charge or series of charges go off, seriously damaging or destroying the building and killing or wounding many onlookers." This is forthright instruction in terrorism, published by the government of the United States.

Other Army-composed passages and manuals are equally instructive. The same booby-trap guide offers methods for rigging bombs to windows and doors, to automobile ignitions, and for concealment in radios, televisions, beds, chairs, sofas, and books. "A book with an attractive cover is sure to invite examination," the manual reads, beside diagrams on how to hollow out pages, insert an explosive, switch, and shrapnel, and rig it with a battery-powered circuit. Among recipes in the Improvised Munitions Handbook are one for fertilizer-fuel bombs, like the one McVeigh used, and one for the explosive concocted by Ressam. David Rohde, a New York Times correspondent, entered Kabul as the Taliban fell and found sections of the Improvised Munitions Handbook in a terrorist group's house, partially translated into Arabic script. Diagrams from its pages also appear in notebooks from camps at Al Farouk, near Kandahar, and in notebooks that I found among Namangani's papers. In another camp, I came across volume one of Al Qaeda's Encyclopedia of the Jihad. Much of it was a direct lift, diagram by diagram — car blasts, door traps, exploding books — from Field Manual 5-31, the U. S. Army's 1965 booby-trap guide.

Hawraman Region, Iraq, December 4, 2002

Northern Iraq had been freed of Saddam Hussein's rule by uprising in 1991. But a new front formed in 2001 when mujahideen and the American-backed Patriotic Union of Kurdistan began skirmishing and reoccupying berms and bunkers from the Iran-Iraq war, now grown over with grass. Two Kurdish garrisons loomed on Gilda Drozna and Tapa Qura, hills rising sharply from the valley floor. The mujahideen charged at the end of Ramadan, when a third of the thirty-five hundred peshmerga posted to the front were on leave and those on duty, wearied by a month of fasting, had gone to sleep. A slaughter ensued.

Kurds who slipped away wounded witnessed executions. Dyari Mohammad said he hid while a friend, Saman, begged for mercy. "He was screaming, 'For the sake of Allah, don't kill me,' " Dyari said. "They took a jerry can of benzene from a Land Rover and poured it on him and set him on fire."

Chang Lee and I had come here to await the war with Hussein, only to encounter the jihad again. This was an enemy that scattered, reorganized, reemerged, a protean force expressed in multiple forms: one day as hijacked planes, another as a car bomber, here a guerrilla force.

The mujahideen withdrew before noon, but their glee was apparent on ground they briefly held. Inside a Kurdish bunker, one had sketched a charcoal portrait of an armed bearded man with vaguely Mongol features, looking sideways, as if pleased. "When we are angry," the artist's script read, "we can't stop our anger."

Sulaimaniya, Iraq, January 6, 2003

I met a mujahideen who suggested the war was my fault. "Osama bin Laden is your son," he said. "You raised him."

The fighter, Sa'ad Mohammad Kasim, was imprisoned with roughly twenty terrorists in a jail the Kurds regard as their version of the American detention center at Guantanamo Bay. Behind one door was a Comoro Islander who admired Jean-Claude Van Damme. Behind the next was a Kurd whom Ansar had sent as a suicide bomber. His bomb had been a dud.

Kasim was a Shia from Baghdad who had been arrested crossing into northern Iraq from Iran. A search of his backpack found a photograph of him in a white skullcap and camouflage attire; he later admitted to spending time in Afghanistan and fighting for Harakat-al-Mujahedin, a terrorist group in Kashmir. He was bizarre and intense, an inmate who annoyed the warden to no end. Sometimes he smiled warmly, then widened his eyes maniacally and whispered threats, then grinned and pretended not to have whispered at all.

The warden of this prison was Colonel Wasta Hassan, a pragmatic former resistance fighter with a dark mustache and a thick mat of black hair. Hassan made for a peculiar American ally: a Muslim who professed hatred of Islam and had internalized his mission so intently that he considered it a duty not just to gather intelligence from mujahideen but to rid them of their faith.

Many inmates submitted to Hassan's will and gave him accounts of their training; a few actively cooperated, providing information about Ansar's defenses, the names and activities of members, and the comings and goings of men who visited Al Qaeda in Afghanistan. The colonel rewarded cooperation with better food and books; one prisoner told me of conjugal visits with his wife.

The colonel hated failure and was prone to dramatic rages and funks. After the attack on the Kurds at Gilda Drozna, he told me Ayub Afghani had recruited fifty people for suicide jobs. One, a teenager, had been captured trying to arrange a meeting with the colonel's boss, at which he planned to explode himself. I met the bomber in an interrogation room. He slumped in a chair and said, "I'm sorry." Later the colonel went to the evidence room and retrieved an explosives-laden vest with a battery pack and a small switch. The bomb, he said, had been made in Afghani's lab at Sarget. "Bastard," he said, and sat slumped like the suspect upstairs. "He is just a boy."

One night, after spending long hours in the jail and enduring a blackout, an unsettling experience in a building full of killers, the colonel let slip that he had attended a government school in Virginia.

So what did you study as a guest of the United States government? I asked.

"English," he said, and laughed a deep, long laugh.

I notice your English is not very good, I said.

"That's what everybody says," he said, and laughed again.

Among the inmates whom Hassan could not break was Qais Ibrahim Khadir, a Kurd with a messianic stare who had been held since an assassination attempt against Barham Salih, the Patriotic Union's prime minister. Two other assassins and five of Salih's bodyguards were killed in the firefight outside the prime minister's front door. Qais admitted killing three guards. Salih had widely known connections to the Pentagon, the State Department, and the CIA, and Qais said he marked him for death because he was "like a plant, watered by the U. S. policy."

Late one night when his jailers moved him from his cell, Qais looked at me and Kevin McKiernan, an ABC News producer, and said, "These men are infidels."

Then he looked at his warden. "You are an apostate," he said. "That's worse."

Hassan was so frustrated by Qais's gloating stoicism — the prisoner remained unfazed after eight months in solitary confinement — that he was considering a new approach. I want to get him drunk and show him pornographic films, he said.

I'll bet you have quite a collection of X-rated films, I said.

"Zora!" Hassan exclaimed. "So much!"

Qais was hardly tempted by flesh. He grinned beatifically at the prospect of paradise and talked comfortably about the possibility of his own execution, saying he had asked his mother to hand out sweets come that day. He marveled at our interest in him, saying no single terrorist is significant.

"Even if Osama is killed, that will not be the end of us, as America knows very well," he said. "This operation will carry on and carry on and carry on."

As Qais saw it, jihad required no command and control. "Al Qaeda," he said, "is a state of mind."

Sarget, Iraq, February 8, 2003

Outside Ansar's cinder-block fortress, Ayub Afghani was telling us this was merely a guerrilla camp. "We have just weapons, and the weapons," he said, gesturing to men with rifles and rocket-propelled grenades, "you can see."

A month earlier, Osman Ali Mustafa, a seventeen-year-old Ansar defector, told me that he had attended a forty-five-day course in this compound with roughly twenty other students and was taught to use infantry weapons and to work with teams on assassination missions called "hit and go." Osman remembered Afghani leading classes. He said it was a difficult course. "It was not only theory," he said. "At night you had to practice what you learned in the morning."

Under ordinary circumstances we would never have come here, knowing what we did of Ansar's ferocity. But Colin Powell's claim before the UN that this was a poison factory had created a desire in Ansar to rebut the charges. Afghani wanted to get the word out.

As he watched, we roamed his camp. If this was a factory, it had no plumbing and little electricity, perhaps the industrial capacity of a primitive campground. But it became clear that Afghani did not want independent inspection. His mujahideen followed us everywhere, blocking doors to certain rooms. Within an hour, patience was gone. One fighter picked up a machine gun and threatened to kill photographers who had strayed from the tour.

Afghani advanced on our group and turned a video camera on us. What do you think now, he snarled, of Powell's "rumor"? He pointed the camera at us, each in turn, thrusting it in our faces, demanding answers. I made eye contact with Jeffrey Fleishman of the Los Angeles Times. He nodded back. Time to go. Afghani pushed the lens toward me. I remembered what these men did to peshmerga, chopping off ears, setting men afire. Fear dried my tongue. "Thank you for letting us do our jobs," I said. We turned slowly, walked to our Land Cruisers, and passed back across the front lines.

Five hours later, three Ansar mujahideen crossed into Kurdish territory to meet a minister of parliament to discuss possible terms for peace. As the minister leaned over a table, writing a letter to refine conditions for a mass surrender, Ansar's negotiator raised a rifle and shot him in the head.

Last year, in the heat of a Central Asian summer, I met an official with the International Committee of the Red Cross who was seeking permission to check on captured mujahideen in one of the region's jails. By this time the Taliban had scattered, and commentary in the United States had lapsed into congratulatory fascination with the campaign's swift success. I asked him what he thought of Washington's war on terror. He gently shook his head. "I am not someone who believes you can kill an idea with a gun," he said.

On my return, I passed through Germany to visit retired colonel Nick Pratt, who had commanded a battalion in the Marine regiment I'd served in more than ten years before. Now a professor at the George C. Marshall European Center for Security Studies, in the shadow of the Bavarian Alps, Pratt teaches courses on terrorism and political instability, drawing on his experience working with the CIA from 1984 to 1987, when he trained mujahideen to fight the Soviets in Afghanistan. He said he worried about the next round of terrorist leaders. "There's something about insurgents," the colonel said. "When they have been beaten over the head, they learn."

As I continued on, through Iran to Iraq to Ansar-held terrain, these two conversations echoed in my mind: You can't kill an idea with a gun. Insurgents learn. They combined to form a critique of the limits of a campaign against an unconventional enemy. And if you carried the notions further, that terrorists were learning, that guns don't kill ideas, that better ideas kill ideas, they prompted questions about what the United States was doing.

After September 11, there was no dispute that a thoughtful military and law-enforcement strategy was necessary to defeat terrorists now at work, and to bring to justice those who had committed so much murder.

Much of what followed is familiar — the seizure of Kabul; the killing of Abu Sabaya in the Philippines; the collection of Khalid Shaikh Mohammed from his bed in Rawalpindi, Pakistan; the escapes of Osama bin Laden and Saddam Hussein as their forces dissipated before the Pentagon and its proxies; the sympathy of Washington's allies giving way to unease about American certitude and might; bombs of makeshift provenance exploding in Karachi, Kabul, Bali, Haifa, and elsewhere; and the establishment by the Associated Press that more civilians were killed in Iraq than had perished at the World Trade Center.

But where was the rest of the plan, the part to address the causes of terrorist anger, and to prevent more young men from joining the fight? There are roughly four hundred million Muslims younger than fifteen. Which way will those on the edge go?

As I sat in northern Iraq, watching the region tilt toward war as surely as it had when I was in the theater in a marine uniform almost twelve years before, it was impossible not to wonder if the United States had entangled itself in precisely the war Osama bin Laden sought, one seen not as extremists against the West, but of the West against Islam — a war that lasts our lifetime and is never won.

Girdi Go, Iraq, March 23, 2003

A Tomahawk missile is a six-yard-long metal tube that flies at more than five hundred miles per hour, guided along its way by an internal computer and map. Each missile carries one thousand pounds of shrapnel and high explosives and fuel for roughly one thousand miles.

At about midnight on March 23, three American soldiers arrived on Gilda Drozna and set up antennas, computers, and radios, on which they began to talk. A short while later dozens of cruise missiles appeared from the west, zooming over farmland and deforested hills and then slamming, in immense explosions, into Ansar's defenses. Peshmerga nearby cheered.

Ansar had anticipated the strikes, not with the precision to know the time of their arrival, but with a soldier's intuition that attack was imminent. Civilians fleeing the area after sunrise said that as missiles arrived, the mujahideen ran from bunkers and buildings and crouched in fields to watch the awesome display. A few were killed. Most survived and were hitching rides to their bases and moving to the front-line village of Khurmal, where gunfire could be heard rippling and popping the next day.

In the morning, Fleishman and I considered entering Khurmal to check on casualties there, but there were only two roads in. One was empty. Listening to the shooting, we decided against it, opting to set up on the last intersection on the other road, which was chaotic and crammed with refugees. It felt dangerous. More journalists arrived, but our Kurdish translators were protesting. We pulled back.

As we left, a Toyota sedan drove to where we had been standing and exploded, blasting fire, shrapnel, and body parts through the checkpoint. We pulled to the shoulder, watching fire and smoke climb in the air above where we had interviewed the checkpoint guards. Cars with shattered windows began lurching away, heading toward us at racing speeds, horns honking, occupants soaked in blood. A man in the bed of a pickup truck was missing the top of his head.

The blast killed the guards we had interviewed and several bystanders, including Paul Moran, an Australian cameraman who had walked into the intersection just as the bomber depressed his switch.

Problems were deepening. Khurmal, the village from where Ansar had sent the suicide driver, was controlled by Komali Islami Kurdistan, an Islamic party that was officially neutral in the fight. Weeks before, a Komali leader, Mullah Abdullah Qasri, and four of his aides had been killed by Kurdish security officers after their Land Cruiser passed by an abandoned Iraqi army base being used by the Special Forces and the CIA. Mistaken for a hit team from Ansar that was said to be casing the American base, Qasri and his entourage were shot top to bottom.

Once the Kurds realized their error, the bodies were turned over to the Komali office, from where Qasri's friends carried them through drenching rain to their mosque and arranged them on the cold floor. Men knelt and closed the dead men's eyes. "They died unjustly for their God," said Fadhil Qaradaghi, a Komali member, waving off condolences. "They were killed because they were Muslims."

Someone's mobile phone rang, filling the mosque with a tune: We wish you a Merry Christmas. We wish you a Merry Christmas.

Komali was still waiting for the results of an investigation into these killings when the cruise missiles struck Ansar. At least two exploded in Komali's barracks. For Komali, the attack was beyond indignity. Its emir, Ali Bapir, had resisted joining Ansar, renounced terrorism, and advocated tolerance of other faiths. Komali also had a treaty with the Kurdish government, which the emir assumed would be honored by the United States. He was wrong. Forty-three of his party members died, killed in their sleep.

The attack against Komali had the feel of a tipping point, quieting the group's moderates and invigorating its extreme. Angry, the party left Khurmal for another village near Iran. As it departed, a group of its members crowded around reporters near the front, where a gunman glared at Fleishman and whispered, "Jewish, Jewish, Jewish."

Beyara, Iraq, March 28, 2003

Mortar rounds boomed and crunched on slopes nearby as Kosrat Rosul Ali, a Kurdish general, led his entourage through the village where Ansar had kept its headquarters. The jihadi brigades had just collapsed. American Special Forces soldiers, who had coordinated the assault and provided air and fire support for it, were busy stowing gear in pickup trucks, preparing to slip back to a safer base.

We had driven with Kosrat through the smoldering Ansar territory, barreling across a battlefield marked with signs of one-sided firepower. Ansar's bunkers, sturdy structures of logs, earth, and bagged sand, had been blown asunder. Roofs were shattered, logs snapped like twigs. Baked soil was lifted and dropped far away, charred gray and black.

Kosrat moved with victorious peshmerga. A wounded fighter, shot through the leg, was carried past him. In a copse of trees beneath him, near a stream, a freshly killed man lay on his back, arms extended upward in rigor mortis. His last apparent effort, raising his hands in self-defense, was useless; the bullet tore through his right pinkie finger and blasted past his ribs. Elsewhere were signs of antics. Someone had tied a captured Ansar flag around the neck of a mud-caked donkey. The creature wandered the gravel road wearing the banner like a cape. The general pulled me aside. "It has been a good day," he said.

In the conventional military sense, the battle had been successful, restoring territory to secular government control. As a counterterror measure, victory was less sure. Kurdish casualty estimates were high, but bodies were few. As in Tora Bora, the Pentagon made a hammer and anvil without the anvil. The United States had chased the jihadis from their camps, but most of them and their leaders had escaped to Iran. Ayub Afghani was not to be found.

As skirmishes continued during the next two days, weary Kurdish fighters walked through Ansar's caves and the remains of Ayub's camp at Sarget. The fortress looked as if it had been stomped by a gigantic boot. The rubble showed that Ayub had not been forthcoming about his camp. Evidence of bomb manufacturing protruded in several spots: a large box with the letters TNT, Italian antipersonnel mines with the explosives scraped clean, inserts for exploding vests. A Special Forces colonel walked by Chang Lee and said, "Tell America we avenged September 11."

Later we walked with Kurdish intelligence officers through Darga Sharkhan, the most secretive of Ansar's camps, where foreign fighters had trained. It was in a deep canyon, a place both sinister and sublime, where calls for prayer had mingled with birdsong and the remains of ancient agricultural terraces marked the slopes overhead. Inside the abandoned academy, an officer picked up a green book, neatly bound, more than 250 pages long.

We flipped through its pages, looking at diagrams — car bomb, pipe bomb, letter bomb, exploding book. I recognized them from before: from Juma Namangani's house in Afghanistan, from the United States government before that — the first volume of the Jihad Encyclopedia, mobile curriculum for international war.

Captured Arabs sat on their knees inside the Baath Party governor's headquarters in a line, heads down, wrists bound behind their backs, facing a wall under the gaze of a portrait of Saddam Hussein. American soldiers and a CIA team looked on. After weeks of aerial bombardment, Kurds and the Special Forces had seized one of the last cities under Baathist rule.

Outside, a celebration churned. Another statue of Hussein had been knocked from its pedestal in the square. Thousands of Iraqi civilians roamed the streets, dancing, chanting, sometimes firing rifles in the air. Slogans appeared on walls in wet paint: VECTORY TO USA. THANK YOU MR. BOSH AND BLEAR.

The captured men were Syrians. They had crossed the border before the war, only to be left alone after Iraqi regulars shed uniforms and melted away.

They sat silently. A few looked defiant. They looked like men who wanted to fight.

A similar scene played out five days later in Tikrit, Hussein's hometown. Kurds and U. S. Marines lounged about presidential palaces, stealing souvenirs and posing for photographs among Jacuzzis and chandeliers, while Republican Guard soldiers lounged in the city among government buildings cracked like eggshells, watching the opening moments of occupation over land they once ruled.

Near the bridge over the Tigris, Second Lieutenant Matthew Peterson paced a broken storefront. "There was fighting to get here," he said. "Now we're just inspecting everybody and letting them come through."

Two doors down, the Iraqi soldiers, tattoos of scorpions on their forearms, sat in civilian clothes, drinking tea. These men looked as though they wanted to fight as well — just not now, but on their terms, some other time and place.

People have faced choices of ideologies before, and Western military commanders have recognized the limits of their guns. In 1947, when much of Europe was in ruins and Secretary of State George C. Marshall was advocating reconstruction and aid, the secretary told a crowd at Harvard that "our policy is directed not against any country or doctrine but against hunger, poverty, desperation, and chaos. Its purpose should be the revival of a working economy in the world so as to permit the emergence of political and social conditions in which free institutions can exist." Not long after, the United States set upon his plan; General Douglas MacArthur was already at work in Japan. Lest anyone think the old generals had gone soft, their efforts were not rooted in mere goodwill. Communism was gaining confidence and power; countries that did not form free institutions and invigorate their economies risked its clutches.

There are similarities today. The Pentagon has demonstrated that whenever Washington decides to rearrange a foreign postal code, it will succeed in pancaking buildings and killing anyone unfortunate enough to be where ordnance finds its mark. That has been the most visible manifestation of a new national counterterrorism strategy released early this year by President Bush. The strategy, which bears the rubric "the 4Ds," seeks to defeat terrorists by attacking their havens and their money; to deny them sponsorship or sanctuary in weak or hostile states; to diminish conditions — poverty, disenfranchisement, poor governance — they seek to exploit; and to defend American citizens and interests abroad. The policy is broadly ambitious and candid at points, noting, for instance, that a solution to the Israel-Palestine conflict is critical to improving the perception of America in the Islamic world. But it is also weighted toward military, law-enforcement, and intelligence plans, a design giving it the lopsided feel of a badly forged sword. It is an extension of the popular assumption that if the United States captures or kills the men who plotted to destroy the World Trade Center, and those who keep their company, then somehow we will have won.

I am not opposed to the use of force; fundamental to Marine Corps infantry service is acceptance of the notion that there are people in the world who would best be shot. But unless defeat is actually balanced with diminish, it is a policy that could ultimately fail. And if the United States hopes to diminish the threat of Islamic militancy over time, it might look to another moment in history when ideologies competed for the loyalty of populations in distress, and develop a strategy to ease a newer manifestation of what Marshall called the "poverty, desperation, and chaos" endangering the free world.

Though different in many ways, the terrorists I encountered are all rooted in societies few would care to live in — undemocratic, corrupt, repressive, stagnant. This is not to excuse anyone for murder, but rather to suggest that if it seems a plausible proposition that a person satisfied in life is less likely to contemplate a suicide attack than someone who is not, then it might be wise to improve social and economic conditions in regions where satisfaction is hard to find.

This is an enormous undertaking. It cannot be realized in an eight-year American presidency. But if the Marshall Plan worked, and it did, then the United States could follow its own example and create a plan to engage the Muslim world on a grand local scale. A productive start would be the creation of a program, akin to a civilian ROTC, underwriting training for Arabic, Pashto, and Farsi speakers schooled in Islamic studies and in professions — hydrology, agriculture, economics, management, journalism, law, medicine — that would allow them to incubate responsive local institutions in Muslim lands.

Recently, the State Department announced the creation of the U. S. — Middle East Partnership Initiative, an effort to accomplish some of these goals. The partnership received $29 million to engage a population of 280 million people, a sum slightly smaller than this year's public-school budget in Arlington, Massachusetts, population 42,389.

Darga Sharkhan, Iraq, April 22, 2003

The Kurdish security officer followed a switchback trail up the ridge, then climbed a slope strewn with boulders and crumbling dirt. Near the top, stone parapets became visible, surrounding a white border marker on the crest. Arriving to the breeze, the officer and I sat in the foxholes among another cache of Ansar's bombs, looking down to Iran, where Ayub Afghani had fled.

Ansar's leadership followed the example of Al Qaeda fighters at Tora Bora, slipping over a border as forward air controllers closed in. The officer said Ayub had rushed from the mosque in Beyara as the ground attack began, followed the cascading green stream below to the border, and talked his way across, where he paid a homeowner a large sum to hide him for a day or two. The Iranians eventually forced most of Ansar's junior members to return, but foreign fighters and Ansar's leaders, including Ayub, were not among them.

Washington had reached the high-water mark of its strategy. Iraq's army and the mujahideen had been forced aside, as had the Taliban in Afghanistan. But the moment the armies scattered, the enemy assumed less detectable shapes, and the Pentagon's firepower met a limit.

The new war was new again. It would now be fought by car bombers in Kabul, guerrillas outside Kandahar, fedayeen near Baghdad, Syrian irregulars near Mosul, Republican Guardsmen in plaid shirts outside Falluja and Tikrit, terrorist cells embedded across the globe. Cruise missiles could no more drive these killers from business than they could chase the Luccheses from New York. The war was not over. Perhaps it was only getting started. I thought of the U. S. Army's booby-trap manuals percolating through the Muslim underworld, of Palestinian bombs continuing to explode no matter how hard Israel pressed, of Colonel Hassan raging about the need to make Qais drink beer and watch pornographic films. Qais had smiled and said Al Qaeda was a state of mind.

I remembered the screech, roar, and rumble of the World Trade Center going down, as if the sky rained trains.

I remembered the colonel and the aid worker: You can't kill an idea with a gun. Insurgents learn. Ayub Afghani had trotted into Iran, below us, because no one closed the back door.

Nearly two years after setting out to avenge September 11, the United States has shown that its might is preeminent, and that with precision weapons or proxies, it can kill Islamic men as it sees fit. Such are the possibilities of power. But it remains an open question whether the sure aim of ordnance is making Americans any safer.

After each pile of rubble is sifted, are there fewer terrorists, or more?